Alpine 3.8 cluster failures #22308

I just added Alpine 3.8 to CI and removed 3.6 in the process, shifting alpine-last-latest-x64 to Alpine 3.7 and giving alpine-latest-x64 to Alpine 3.8. It tested well on my local machine across our major branches, but now it's enabled in CI we're getting consistent errors with on all test runs:

15:57:44 not ok 647 parallel/test-cluster-master-error
15:57:44   ---
15:57:44   duration_ms: 120.63
15:57:44   severity: fail
15:57:44   exitcode: -15
15:57:44   stack: |-
15:57:44     timeout
15:57:44   ...
15:57:44 not ok 648 parallel/test-cluster-master-kill
15:57:44   ---
15:57:44   duration_ms: 120.92
15:57:44   severity: fail
15:57:44   exitcode: -15
15:57:44   stack: |-
15:57:44     timeout

What should we do with this? Do I remove it from CI for now or can someone spend some time investigating?

The Dockerfile is here minus the template strings which you can easily stub out to set this up locally if you want to give that a go. I'm not sure what the difference is with my local machine but perhaps I wasn't testing it on the latest master and there's something new or perhaps there's a Docker differential.